France has hit out at a Reform UK plan to return migrant boats using the Navy, saying the proposals would violate its sovereignty and breach international law.

Nigel Farage’s party announced earlier that if it was in power it would intercept boats crossing the English Channel and return migrants to French ports, even if France disagreed.

Opposition parties have branded the plan unworkable, while a Labour minister said it would lead to “a lot of time arguing with France” instead of “actually getting to grips with the problem”.

Speaking earlier, Farage said he was “entirely confident” the plan could be justified under international maritime law.

Under the plans, which Reform said it would bring in if it entered government after the next election, military-crewed inflatable boats deployed from 10 Navy patrol vessels would be used to “come alongside” migrant boats crossing the English Channel.

Border Force officers and police stationed onboard would be tasked with arresting people in the boats, and they would then be returned to France or Belgium by Navy personnel or Marines.

The party said returns operations would be conducted by military personnel with Border Force officers on hand in case of “non-compliance”, with a Bay Class landing ship providing “detention capacity at sea” for up to 700 people.

Speaking at a news conference on Monday, Reform’s home affairs spokesman Zia Yusuf said the party would aim to get agreement to disembark arrested migrants at French ports.

He added: “If the Elysee Palace refuses, make no mistake – His Majesty’s Royal Marines will disembark them safely on the very shore they left that morning”.

Speaking alongside him, Farage played down the prospect of a diplomatic confrontation with the French, claiming that attitudes in France towards the idea were “softening”.

But in a statement issued later on Monday, the French interior ministry said: “This would constitute a violation of French sovereignty, as well as a violation of the law of the sea and international law.”

A spokesperson for the department added that measures agreed with the UK, as well as “operations deployed at the local level”, had already led to a reduction in crossings so far this year compared to the same period in 2025.

In a policy document, the party argued the plan would be legal under international law because it would be protecting the lives of migrants in dangerous boats.

It cited the United Nations Convention on the Law of the Sea (UNCLOS), which talks of a duty on states to “render assistance to any person found at sea in danger of being lost”.

Farage said he was confident his party’s policy of “securely picking people up and safely taking them back to France” would fall within “other conventions of international law”.

Yusuf accepted the plan could trigger a “diplomatic argument” with France, but insisted it had a “commitment under international law” to process migrants.

Andrew Serdy, an expert on the public international law of the sea at the University of Southampton, argued Reform’s proposals “would require the agreement of France, which is a bold assumption to make, as there is no reason to expect it to agree.”

James Turner KC, a lawyer at Quadrant Chambers with expertise in maritime issues, told BBC Verify that UNCLOS gave states rights to prevent infringement of its immigration laws in a “contiguous zone” up to 24 nautical miles from its coast.

However, he added this did not entitle countries to “collect asylum seekers in its contiguous zone – or anywhere else – and take them back to the state they set off from”.

More than 2,000 migrants have arrived in the UK on small boats since Andy Burnham became prime minister two weeks ago, and 326 people crossed the English Channel on Saturday. Home Office figures show crossings so far this year are down around 43% compared to the same period in 2025.

The number of small boats crossing the Channel have been on an overall downward trend since it peaked in 2022, Home Office figures show.

Speaking earlier, Energy Secretary Miatta Fahnbulleh said the Labour government’s push for greater action against smuggling gangs was a “model that is working”.

She added that she did not believe Reform’s plan would work, citing the involvement of the Navy as an example of “gimmicky” ideas explored by the previous Conservative government.

“You’d spend a lot of time arguing with France, and not enough time actually getting to grips with the problem,” she added.

The prime minister visited Dover at the weekend, where he said the government was “changing the whole approach” to small boats, as the numbers of enforcement officers tackling people-smuggling gangs doubled on both sides of the Channel.

According to the Home Office, the number of National Crime Agency (NCA) officers tackling smuggling gangs facilitating small boat crossings had risen to almost 800 from 376 at the start of 2025.

Conservative shadow home secretary Chris Philp said Reform’s plan was not “credible”, adding: “They can’t answer the question how they would disembark immigrants back in France if the French don’t agree”.

“Reform’s policy I am afraid as usual is on the back of a fag packet”.